Woody biomass is a core element of our nation's strategy to replace imported oil and natural gas with renewable resources. Approximately two hundred million tons of wood waste is generated by the forest products and paper industries, most of which is being used for co-products or energy. Additionally, more than one hundred million tons of woody biomass is available, but not currently used, per year from forest management, wildfire fire protection, and urban woody debris. As forested landscapes in rural and urban areas are more intensively managed in the future, the amount of available woody biomass will increase.
Woody biomass has low bulk density, and so machinery has been developed to collect and compact woody biomass into transportable bundles, bales, modules, and containers. Pioneering research was undertaken in Scandinavia (Mäkelä 1975; Danielsson 1977; Carlsson 1980; Säll 1981; Larsson 1981) and Canada (Sinclair 1981; Jones 1981a, 1981b).
In the United States, Dr. Awatif Hassan at North Carolina State University early on investigated the energy consumption for a wood chip compaction system (Hassan 1976). Dr. William Stuart at Virginia Polytechnic and State University was among the early U.S. developers of forest biomass balers (Stuart and Walbridge 1978). His baler was brought to the University of Washington in 1982 for testing by Dr. Peter Schiess (Schiess and Yonaka 1983). Concurrently, James Fridley and Dr. Thomas Burkhardt at Michigan State University worked to adapt round agricultural balers to handle forest biomass (Fridley and Burkhardt 1984). Unfortunately, both projects stopped when the price of oil began to fall and public interest in biomass energy waned.
Fortunately, much of that initial flurry of research was documented in conference proceedings and review articles (Sturos 1982; Guimier 1985). Guimier compared the potential of five existing systems (round agricultural baler, square baler, garbage truck, garbage compactor, and cotton module builder). His team found that square bales of the type made by recycling balers and large cotton modules showed the most promise.
Renewed interest in woody biomass as a fuel and feedstock during the 1990's stimulated a number of development programs around the globe. Baling, chopping, and intermodal bulk hauling are being concurrently developed, with each being an optimal solution for particular circumstances. Chopping and intermodal bulk hauling are particularly attractive for very short haul distances. However, once the haul distance exceeds about 35 miles (60 km), the need for high bulk density solutions becomes apparent.
Baling woody biomass to achieve high bulk density is being pursued by three technical approaches, again each approach being preferred for particular situations. Timberjack, now John Deere Forestry, has commercialized a biomass bundling system that was developed in Finland to enable forest materials to be handled similar to logs. Dr. Philippe Savoie's team in Canada has been developing round baling for woody biomass crops such as willow (Savoie et al. 2006), and more recently with SuperTrak has adapted the round bale technology for use in forestlands to cut and collect understory saplings and brush. Round bales can be collected, transported and handled like round bales of hay. The third technology, rectangular balers is the subject of this patent application.
The present inventors have reported their progress under a federal contract from the USDA CSREES SBIR program to develop better methods to collect and transport woody biomass (Dooley 2006; Lanning 2007; Dooley 2008; Dooley 2009). Our goal has been to engineer more efficient recovery and transport of woody biomass to second-generation bioenergy and biofuel plants.